Field
The following description relates to a thermoelectric device and a method of manufacturing the same, and more particularly, to a thermoelectric device and a method of manufacturing the same, capable of securing improved mechanical strength and generation efficiency.
Description of the Related Art
The Seebeck effect is a phenomenon by which an electromotive force is generated by the presence of a temperature difference in the natural world, machinery, buildings, artifacts, etc. If an energy generation device based on the Seebeck effect is used to provide electrical energy in various types of electronic products, battery life is increased. Further, an electronic product having low power consumption does not require battery replacement or does not require a battery at all.
The electromotive force generated using the Seebeck effect has an output voltage on a scale of millivolts. Accordingly, in order to obtain a desired level of voltage from a thermoelectric device, a plurality of thermopiles in the thermoelectric device are electrically connected in series and thermally connected in parallel.
When a thermoelectric device is manufactured by thin film processing, the electrical and thermal connections of the thermopiles are achieved by a single process using one the same conductive material for both electrical and thermal connections. That is, a plurality of thermopiles are formed on a lower wafer by thin film processing, and the lower wafer with the thermopiles is bonded to an upper wafer such that the thermopiles are electrically connected in series and thermally connected in parallel. In the bonding of the wafers, a soldering material or a conductive polymer material is used. However, such an adhesion material for bonding has a relatively high electrical resistance, which increases the total resistance of the thermopiles that are electrically connected in series.
A typical thermopile, which is manufactured through a thin film processing, has a small cross section and a large length which increases the thermal resistance of the thermopile. However, since the thermopile provided in the form of a thin film also has a low mechanical strength, the mechanical strength of a bond is not secure when another wafer is bonded to a wafer on which the thermopiles are formed. In addition, a bonding pressure may cause process faults, such as breakage of the thermopiles, so that the yield of the thermopiles is lowered. Even in a case in which the bonding process is successfully achieved, a rigid material, which is inserted between the upper and lower wafers to reinforce the mechanical strength when using thermopiles, forms an additional heat transfer path between the upper and lower wafers. In contrast, in order to maximize generation efficiency, the heat received from the lower wafer needs to be transferred to the upper wafer through only the thermopiles themselves. If the heat is transferred to the upper wafer through the supplementary material inserted between the upper and lower wafers, the generation efficiency is lowered.